The present invention relates to a method of centering and mounting a light waveguide or optical fiber in a sleeve, and more particularly to a centering and mounting method of the type wherein the sleeve is composed in part, at least at one end face, of a body of ductile material having a bore which is coaxial to the sleeve axis, the light waveguide is pushed into the body, and an upsetting tool is employed to exert pressure onto the end face of the body. The invention also relates to a sleeve which includes a waveguide that has been centered and fixed, and then cut off flush with the end face of the sleeve. The invention further relates to an apparatus of the type which includes an upsetting tool.
European 94,906 discloses the centering and mounting of a light conductive fiber in a light waveguide end piece, with the fiber being freed of its protective layer and being pushed into a centering cylinder. The centering cylinder is composed of a hollow cylindrical outer member made of a relatively hard material filled at least in the region of the end face with a core member of a plastically deformable material. The core member includes an axial bore to accommodate the fiber end. An annular upsetting tool is pressed against the end face of the core member so that the upsetting tool concentrically surrounds the bore holding the fiber and the material around the fiber is plastically deformed, thus fixing the fiber end centrally relative to the outer faces of the centering cylinder.
The centering and mounting of the fiber is thus effected by a symmetrical pressure on the end face of a ductile core member. In this process, slight residual deviations cannot be avoided. However, these residual deviations may have a negative effect, particularly when monomode fibers are mounted. For example, light losses may occur if two monomode fibers mounted in this manner are fixed one on top of the other in a groove accommodating the two centering cylinders.
German Patent 3,442,822 discloses a method with which an already-fixed light conductive fiber can be accurately centered in the sleeve. To accomplish this, a pressure that is asymmetrical relative to the sleeve axis is exerted on the core member. This pressure produces a radial displacement and the light waveguide end section is finely adjusted relative to the sleeve axis.
U.S. Pat. No. 4,763,980 also discloses the centering of a light conductive fiber by eccentric pressure from a tool acting in the axial direction. Initially, the light conductive fiber is fixed and preliminarily centered by means of an annular upsetting tool and then it is centered by means of a segment-shaped upsetting tool.
The light waveguide is thus mounted and centered in the sleeve in a two step process. First, an annular upsetting tool is used to provide the fixing. Then a further upsetting tool exerts an asymmetrical pressure and thus finely adjusts the light waveguide. This procedure has the drawback that two process steps are required. Another drawback is that the light waveguide is fixed by pressure onto the ductile core member by means of the annular upsetting tool over only a very short section of the core member, at its end face. This can be compensated by gluing the light waveguide in the bore over the rest of its course. However, fine adjustment is possible only as long as this adhesive has not set. The low penetration depth of the annular upsetting tool, and thus the small region in which the fiber is fixed, is particularly disadvantageous if the sleeve including the core member (which is made of a deformable material) and the light waveguide are to be ground after the light waveguide has been fixed. This is necessary in order to obtain a planar end face and a light waveguide that is embedded therein in a planar manner. If, however, the light waveguide is fixed only over a small region at the end face, the danger exists that the grinding may destroy the attachment.